The human T-cell leukemia viruses (HTLV) comprise a family of exogenous human retroviruses. HTLV type-I (HTLV-I) is etiologically associated with adult T-cell leukemia-lymphoma (ATL), first described clinically in Japan and found endemic to southern Japan, the Caribbean Basin, and certain parts of Africa. HTLV type II (HTLV-II) was isolated from a patient with a T-cell variant of hairy cell leukemia. Despite divergence between HTLV-I and HTLV-II, they are conserved to the extent that they are serologically cross-reactive. A third subgroup of HTLV (HTLV-III or HIV) refers to a virus isolated from patients with acquired immune deficiency syndrome (AIDS).
Specific antibodies to HTLV-I have been detected in ATL patients and in asymptomatic carriers; and in patients with tropical spastic paraparesis and with HTLV-I associated myelopathy. These antibodies are known to recognize both gag and env protein of the virus. Viral gag proteins have been purified, sequenced, and murine monoclonal antibodies against these core proteins (p19, P24) have been produced and extensively used for detecting core antigens. Murine monoclonal antibody to a minor component of envelope protein (gp 21 or p20E) has been reported. Recently, a monoclonal antibody (mAb) designated 0.5.alpha. has been produced to the major component (gp46) of the envelope glycoprotein (env). (See U.S. Pat. No. 4,722,888). Antibody from the cell line 0.5.alpha., described in U.S. Pat. No. 4,722,888, binds specifically to the major HTLV-I envelope protein (gp 46). However, the specific epitopic site for binding of the antibodies secreted by cell line 0.5.alpha. has not been reported previously.